[Closed] How fast do you need to be going to get airborne on a bike

You can't really put a number on it - depends on the rider. As an example, at Wind Hill the good kids can clear the bigger doubles and tables without needing much speed. Whilst I can clear them as well, I need a lot more speed as my technique isn't as good.

JP

That's why I'm kind of wondering what sorts of numbers are involved.  Some people seem to be hardly moving at all and I don't know if that's actually true or if they just make it look effortless but are still moving swiftly

Shirley more pump than speed.

Watch Danny Macaskill and he gets vertical with no forward momentum.

Doesn't matter for me - I fly like a wounded heffalump

ok, I'm going to actually have to do some  nummmmbers aren't I 🙁

It really does look like it depends on how much height you can get when you pop up.  If you can get 50cm then you only need to be travelling at 12km/hr to go 2m.  If you can only get 20cm then you need to be doing 18km.hr horizontally

more pop, less speed I guess.

Depends how much "pop" you can generate.

It takes a given amount of energy to get a rider of a known weight over a known distance.

That energy is a result of "pop" and speed. More pop, means less speed is required and vice versa.

If you want numbers, according to my data I'm hitting 39km/h before the first of the three bigger tabletops on Emperu at Wind Hill. That's landing quite far on the downslope, which is a jump of several meters, without needing to pop a huge amount.

JP

Depends how much “pop” you can generate.

It takes a given amount of energy to get a rider of a known weight over a known distance.

That energy is a result of “pop” and speed. More pop, means less speed is required and vice versa.

this

a mate knacked his wrist at the '97 Nationals. Rode the DH race bandaged up, basically one handed. There was a set of doubles at the bottom, and he trundled up to it pretty slowly. We all expected him to roll over it, but he just gave it a bit of a pump and cleared them easily. Quite an eye opener, very impressive!

Its not just pop though its also how much you push through. You can force yourself to high and reduce how much you move forward or go low and long and keep the momentum going forward.

If you want numbers, according to my data I’m hitting 39km/h before the first of the three

Thanks that's very helpful.  I really don't aspire to doing that except in my dreams but it's good to know

Its not just pop though its also how much you push through

Yep.  I didn't try and deal with that when doing a quick calc.  I was just trying to get an idea of how fast was really needed as a basis.

There is an episode of Seth’s Bike Hacks where he takes an old BMX friend mountain biking for the first time.
The guy was clearing stuff (whistler bike lark) at really slow speeds. Experienced mountain bikers following were casing badly at the same speed.
It was all down to pop and technique rather than speed for him.

My son can get "air" off a 2 pence piece on the tarmac, tis not about speed but the roll of hips and wrists

Shirley it depends on how fast the treadmill is moving?

I took a trials-riding mate DHing once. He was clearing doubles at ridiculously low speeds, it really made me realise how much I was relying on speed rather than technique.

So yea, speed is only one part of the equation.

I've been wondering this too. You need to bunnyhop of the lip of the jump to get distance. It's what is holding me back from jumping doubles.

So yea, speed is only one part of the equation

Agreed.  I wasn't until I looked at the numbers that I realised just how big the difference was really.  It really does seem to be more about take off technique than hitting a bump at the correct speed.

Different people, different ways of thinking about things

Hate that gif Kayak, basically claimed the life of a great BMX'er (Colin Winklemann).

Oh dear. Had no idea, sorry 😥 Can't remove it now.

Report it and mods will sort it

Less than 88mph.

Oh dear. Had no idea, sorry

No problem, most people wouldn't know the backstory. Winklemann broke both his legs badly enough that he couldn't ride again, he ended up depressed and took his own life.

I keep coming up short just on tabletops. I naturally suck the jump up which is only good if you want to flatten it. So I've been focusing on popping off and this is going well, but I know I need to learn to bunnyhop before I can easily clear things.I've seen all the tutiorials and still cannot do it. I am wondering if it's because I am short and do not have enough leverage in my legs and arms but I will keep practicing anyway on my bmx. Also you need to bunnyhop with your legs ending up stretched out, rather than scooping the rear up with your feet. This is so if you come up short the extended legs can be used to soak up the landing.

If you are on a FS OP you need to compress the shock on the upslope and make sure you rebound is set up fine so it does not pogo you off.

I fly like Steve Austin before he got his upgrades!😁

if for the purposes of simplification we ignore anything like air resistance, or drag, then gravity is an acceleration of 9.81 meters per second per second. i.e. you are being pulled towards the centre of the planet by a force that would change your velocity by 9.81 meters per second (35kph / 22 mph) for each and every second that it acts

So, if you jump upwards, so that just as your feet leave the ground you whole body is going directly upwards at 9.81 m/s, then it'll take 1 second for gravity to slow you to zero speed, and in the next second it'll re-accelerate you back to 9.81 m/s, so just as your feet touch the floor again, you'll again be going 9.81 m/s but in the opposite direction. The total "air time" is obviously 2 seconds (1 sec up, 1 sec down)

So, if instead of standing still, you are moving laterally, then you'll move the distance that is your velocity multiplied by your air time. So, if you are travelling laterally at 10 m/s, and you leave with 10m/s of vertical velocity you'll be 20 (66 feet!!) meters away when you land (a long way!)

Now for a real "jump" on a mountain bike, your velocity vector is a combination of the angle of the take off ramp (needs to be at 45deg to the horizontal for the farthest distance for any given speed) but because you can either "spring yourself upwards" or "absorb" some of the upwards movement from the ramp with your leg, we need to consider those effects, which are broadly what people call "popping" or "squashing" a jump.

Now, for most people, there is a natural limit to just how fast they can spring up and off the ground, so for "slow" jumps, how much you pop makes a significant difference to the distance traveled, because the upwards speed your pop provides is a large proportion of the total upwards speed. However, for large high speed ramps, it's the shape and steepness of the ramp that does the work. This is really what makes some jumps 'easy' to ride and some 'hard' to ride. Go to a bike park with massive (say 5 or 10 bike lengths long) well shaped jumps that are nicely fitted to the natural speed of the trail, and to clear them, really, you don't do much, it's all done by the ramp. But slow, short, steep, and especially 'lippy' jumps are a different matter entirely and require the rider to both provide some of the lift and also to correctly manage the bike in the air (ie to match the angle of the landing ramp). The shorter and the steeper the ramp, the more you will have to do as a rider to smoothly follow the invisible "parabola" of the jump.

(worth noting that jumps that are step-downs, ie have a landing lower than the take off, or step-ups (landing > takeoff) need to be considered as of a different 'length' than a jump with a level take off and landing, for what should be obvious reasons.... 😉 )

As with Steve. RIP colin winkleman.
Don't feel bad for posting it kayak, you obviously didn't know.

As for actual speed numbers for tabletops at trail centres?
Depending on how nice the lip is a bike length trail centre table can be pumped and boosted to downslope at walking pace by any decent jumper. but if the tabletop is part of a faster trail, faster more skilled riders will be hitting them far faster and squashing/scrubbing (perhaps even manualling and not jumping at all) to stay low and get the wheels back down sooner.
Whereas something like a 40' gap does need to be hit at above a certain speed. But this stil ldepends on the rider and the actual shape of the jump. Not that i've ever checked the speed but the 40'er on Zore (Super Morzine) for example is a straight no pedalling rollin with the tiniest brake check (or air brake) just before the lip for me so I'd put that at probably just under 30mph.
Tables, step ups and step downs/Fades all require different approach speeds. Luckily most trail centres these days are built by folk who understand flow so if you're hitting the first jump at an appropriate speed to clear it it should follow that you'll make all of them.
Any proficient jumper can adjust on the lip and in the air to land on downslopes smoothly at a fairly wide range of approach speeds.

Definitely spend time learning proper bunnyhops before worrying about jumping. This will teach you how to preload properly, how to level out and nose in and teach you how your feet placement and body position should be. By learning. I mean practice until you never have to think about it at all. and it has become natural and ingrained in muscle memory.

None of this... I went to see a skills coach and I now know what to do and regurgitate it on forums pish. Get out and repeat the maneouver all the time. every time you can.

**** me. am I psychic?

Hate that gif Kayak, basically claimed the life of a great BMX’er (Colin Winklemann).

+1 real sad clip to see. It's one of those horrible changing points in someone's life.

btw, in part two we will calculate the energy you absorb when you come up short and land on your head.......... #physicsisfun 😉

https://en.wikipedia.org/wiki/Projectile_motion

Report it and mods will sort it

Can someone else do that please? Can't report my own post seemingly.

Definitely spend time learning proper bunnyhops before worrying about jumping

That's the conclusion I came to as well.  It's sort of obvious really but I needed some numbers to get it

0mph

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